3
votes
1answer
100 views

One-time pad mistake in the transmission?

I have a question which arised by analyzing the one-time pad cipher. I encrypt a binary sequence $a_1,a_2,..,a_N$ using a one-time pad with key sequence $k_1,k_2,k_3,...$, so I send $a_1+k_1, ...
3
votes
4answers
346 views

Is there a way to generate sound one-time pads out of public information?

Is there a way to 'mangle' a public data-source (for example, the current date in YYYYMMDD or the top New York Times headline) to form a one-time pad that will sufficiently hide the pad's source? ...
2
votes
1answer
167 views

Diffie-Hellman: Does the size of the prime modulus depend on the potential size of the secret?

I'm writing my own cryptosystem that uses One Time Pad and Diffie-Hellman to generate keys for the OTP. I am using Rails on the server side and Javascript for the client side. Please don't tell me ...
4
votes
1answer
189 views

Can two people with different one time pads securely exchange a message like this?

Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his own one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts ...
1
vote
2answers
183 views

Re-using parts of a one time pad to encrypt a new one?

The main problem with OTP's is the fact that they can only be used once. Would it be possible to use a random number that's, say, 512 digits, then use 256 of those for the (non-random) message, the ...
1
vote
4answers
851 views

“Padless” One-time-Pad encryption

I have just read about the perfect security of an OTP encryption and what came to my mind was that what if the Pad used for encryption/decryption did not have to be transported separately from the ...
2
votes
2answers
565 views

Avalanche noise RNG for one-time pad use

I came across this little HRNG widget and was really intrigued as I have been looking for a decent but afordable source for truly random bits to use in a one-time pad. The question is, would a HRNG ...
4
votes
2answers
1k views

Perfect security definitions

In my notes, there are 2 definitions of perfect security: "For $M \in \{0,1\}^m$, define the distribution $D_M$ on strings as follows: to choose a random member of $D_M$, choose a random $K \in ...
2
votes
1answer
750 views

One-time pad and zero key

I'm doing some exercises before my exam, and I am stuck with task number 4 in this file: http://www.cs.umd.edu/~jkatz/crypto/f10/hw1.pdf Could you help me with this task? When using the one-time ...
2
votes
2answers
797 views

Difference in one time key and one time pad and many time key

These terms are confusing me. One time pad is when you use one key for one message. That is what One time key is. Secondly, what is the connection of many time key, can i use one time pad many ...
9
votes
4answers
2k views

What is the difference between a stream cipher and a one-time-pad?

A (synchronous) stream cipher is an algorithm which maps some fixed-length key to an arbitrary-length key-stream (i.e. a sequence of bits): $C : \{0,1\}^k \to \{0,1\}^{\infty}$. This key-stream is ...